Determine the empirical formula of the compound with a crystal structure where silver ions occupy one‑half of the tetrahedral holes in a cubic close‑packed (ccp) array of iodine anions.

there are two significant figures.

alchemy hadn't scientific methods of study, appeal to mysticism and fantasy, the knowledge of chemistry and physics were modest at that time.

alchemy was - but as new rules were discovered it either changed into chemistry or it became "unscientific".